The present invention relates generally to structural metal plates and, more particularly, to a corrugated structural metal plate that is curved about an axis transverse to its longitudinal axis for use as a load-bearing member.
Structural metal plates are often used as load-bearing members in underground tunnels, culverts and large diameter pipes, for example. Typically, structural metal plates include longitudinally extending sinusoidal corrugations defined by alternating crests and valleys to increase the load-bearing capacity of the plates. The structural metal plates are commonly bent or curved about an axis transverse to the longitudinal axis of the plate so as to have an arcuate curvature in the longitudinal direction. For example, several curved structural metal plates may be connected end-to-end to form a section of a large diameter pipe. Each ring-like section is joined along longitudinal edges of the plates to an adjacent section for forming the desired pipe structure.
During the curving process, one side of the plate is subjected to forces of tension, while the other side is subjected to forces of compression. These forces are separated by a xe2x80x9cneutral bendingxe2x80x9d axis so that forces of tension occur on one side of the neutral bending axis toward the outside of the curve while forces of compression occur on the other side of the neutral bending axis toward the inside of the curve. Generally, corrugated structural plates exhibit optimum elastic and plastic strength when the neutral bending axis of the plate is coextensive with a vertical midplane of the plate. At this position, the distance from the neutral bending axis to the maximum tension fiber and the distance from the neutral bending axis to the maximum compression fiber are the same. To achieve optimum elastic and plastic strength, structural metal plates are typically formed with equal numbers of substantially identical corrugations on each side of the vertical midplane of the plate, thereby locating the neutral bending axis at the vertical midplane of the plate. However, such a design limits the minimum radius to which the plate can be curved without buckling on the compression side.
Thus, there is a need for an improved corrugated structural metal plate that can be curved to a desired minimum radius without buckling on the compression side of the plate.
The present invention overcomes the foregoing and other shortcomings and drawbacks of corrugated structural metal plates heretofore known. While the invention will be described in connection with certain embodiments, it will be understood that the invention is not limited to these embodiments. On the contrary, the invention includes all alternatives, modifications and equivalents as may be included within the spirit and scope of the present invention.
The corrugated structural metal plate of the present invention is particularly adapted to be curved from a generally flat configuration to include an arcuate curvature in its longitudinal direction without buckling on the compression side of the plate. The structural metal plate of the present invention includes longitudinally extending corrugations that are defined by alternating crests and valleys. In accordance with the principles of the present invention, each crest is in tension when the structural plate is curved about an axis transverse to its longitudinal axis and includes a substantially flat segment extending longitudinally along the crest. Each valley is in compression when the structural plate is curved and includes a substantially flat segment extending longitudinally along the valley. Preferably, a pair of longitudinally extending curved segments are formed along opposite sides of each flat segment formed on the crests and valleys. Each corrugation preferably further includes a longitudinally extending, substantially flat segment formed between and interconnecting the curved segments.
To avoid buckling on the compression side of the plate when the plate is longitudinally curved, the flat segment formed along each valley has a cross-sectional width that is less than a cross-sectional width of the flat segment formed along each crest. The cross-sectional width of the valley flat segments is selected to permit the plate to be curved to a desired minimum radius without buckling. To prevent the neutral bending axis of the structural plate from being displaced away from the vertical midplane and toward the valleys of the corrugations, the plate is formed with an unequal number of crests and valleys. More specifically, the structural plate of the present invention includes at least one more valley flat segment than crest flat segment. As a result of the unequal number of crests and valleys, in conjunction with the relative cross-sectional width dimensions of the crest and valley flat segments, the neutral bending axis remains generally coextensive with the vertical midplane of the plate after the plate has been curved to the desired minimum radius to optimize its elastic and plastic bending strengths.
The above features and advantages of the present invention will be better understood with reference to the accompanying figures and detailed description. It will also be understood that the particular drawings illustrating the invention are exemplary only and are not to be regarded as limitations of the invention.